1. Field of the Invention
The present invention relates to image processing apparatuses.
2. Description of the Related Art
As a compression-encoding method of images, object encoding has been conventionally known. In object encoding, the foreground and background of a plurality of continuous frames of images (one scene or one cut of image) (for example, frames from a scene change to the next scene change) are extracted. When a plurality of images are formed of N frames, the background (if a scene is taken when a video camera is panned or tilted, for example, the background is a landscape image or a portrait image) of the entire one scene displayed by the N frames and the foreground obtained in the N frames in common are extracted. Data obtained by object encoding is decoded by arranging the foreground in the background. This type of object encoding is described in U.S. Pat. No. 5,706,367, assigned to the assignee of the present application, and hereby incorporated by reference.
In encoding in which the foreground and the background are extracted, such as object encoding, the way the extracted foreground is encoded highly affects the efficiency of encoding.
In encoding in which the foreground and the background are extracted, such as object encoding, the precision of extracting of the background highly affects the quality of the decoded image.
As a method for detecting camera motion in object encoding, a method for regarding the entire frame as one block and achieving block matching can be considered, like a method for detecting the motion vector of a macroblock.
To apply block matching to the entire frame, however, it is necessary to obtain the sum of the absolute-value differences between the pixels of an image on one frame and those of an image on a frame one frame before while the spatial position of the frame for which camera motion is to be detected is being shifted. The amount of calculation is huge and the calculation is troublesome.